Beam deflection control for cathode-ray devices



2 Sheets-sheet 1 Jan. 25, E949. A. wRxGHT ET AL BEAM DEFLEC-TION CONTROL FOR CATHODE-RAY DEVICES Filed sept. 2s, 1946 llwv.

A. WRIGHT ET AL BEAM DEFLEOTION- CONTROL FOR OA'THoDE-RAY DEVICES Jan. 25, 1949.

2 Sheets-Sheet 2 Filed Sept. 26, 1946 M? www .M N N .m MW E Patented Jan. 25, v17.949

SATES PATENT OFFICE- BEAM DEFLECTION CONTROL FOR CATHODE-RAY DEVICES Antony Wright, Drexel Hill, Pa., and Edwin L. Clark, Collingswood, N. J., assignors to Radio Corporation of America, a corporation of Dela- Application September 26, 1946, Serial No. 699,536

i Cl. 315-22) 16 Claims.

l This invention is directed to electronic circuits for use particularly in relation to the control of the deilection of a cathode ray beam developed lograph devices where electron beam deflection is controlled from an external source.

Particularly in connection with television developments, it has been found that in order to provide satisfactory images for viewing at the receiving point, the synchronization must be maintained very accurate at all times. Accordingly, noise disturbances, such, for instance, as those due to ignition troubles introduced from nearby disturbing sources or even remote sources may frequently have a very detrimental effect on the viewed image. Where there is a disturbance effect on the deflection, due to ignition noises, many times due to the effect of diathermy and other forms of spurious signals, the resultant disturbances, all of which will hereafter be referred to for convenience as the noise signals,

frequently add to the synchronizing pulses, ordinarily termed the sync pulses, and destroy both the synchronization and interlace of the viewed image. Further, the noise signals, when combined with the sync signals, or when occurring immediately prior to the time of receipt of sync signals, often cause the local oscillators or sync control channels to trace or trigger at times which precede the desired sync pulses and, thus, frequently cause diiferent scanning paths, which, literally, tear out and destroy the resultant image.

Accordingly, it becomes one object of this invention to provide a system for synchronizing television or oscillographic apparatus which will have a high degree of immunity to noise impulses.

A further object of the present invention is that of providing a synchronizing system in which it is possible to retain the maximum resolution of image detail under conditions of low signal-to-nolse ratio, since it has been found that the apparent resolution oi an image is very greatly improved where the synchronizingeects are rigorously held to some predetermined standard and constant rate.

control of the electron beam deection oi an image producing cathode ray tube which will preserve the desired line structure of the image raster irrespective of the inuence of electrical disturbances.

Other 'objects of the invention are those of providing improved forms of synchronizing action wherein the elects of received snychronizing pulses may be, in elect, heldover or subjected to what might be termed flywheel action, whereby only the desired sync signals Shall have effect on the control and the operation of the deection channel.

Other objects of the invention are those of l providing a television circuit particularly useable in the deflection channel which shall embody the principles of an automatic frequency control operating in such a way that the deection is improved to a considerable degree over that normally obtainable with the so-called triggered Another important object of the invention is synchronizing circuit control.

Other objects vof the invention are those of providing an improved form of deection control and synchronizing circuit which has greater eiiiciency in its operation; is more stable in its control; is relatively cheap to construct; is positive in its operation; and, Aat the same time, overcomes many defects heretofore found to exist in prior art arrangements.

Still other objects of the invention will become apparent and suggest themselves to those skilled in the art to which the invention is directed when the accompanying drawings are considered in the light of the description to follow.

In the drawings, Fig. 1 represents in block diagrammatic form one suitable circuit by which the invention in question may be practiced;

Fig. 2 is a circuit wherein the principles of Fig.l

1 are incorporated;

Fig. 3 comprises two curves to show the operation of the system under one condition;

Fig. 4 consists oi a set of two curves to show the operation of the system under other conditions; and

Fig. 5 represents a modification of the circuit v put to control a scanning oscillator, the output of which, in turn, Was fed back to the phase' detector. In this way, essentially a triangular opment of substantially sine wave voltages which..

are relatively easy to control',whi`cli. can. readily be stabilized, and which may serve. aslthetrig.-

gering control instrumentality by which a subtantially normally and customarily used form .of sawtooth wave generator mayI be' controlled 5to` supply its output to the normal power output tube for controlling the cathode ray beam delec* tion in at least-one direction on the image raster.

The invention las disclosed,v particularly by the block diagram arrangementofFigj. 1', andas it willb'e described in later reference. herein to `that figure, comprises essentially lthe combination. of Y a stableoscillaton a reactance tube`connected inlshunt' with the oscillator, and a discrimi'nator network adapted to receive sinusoidalY wavesfrom` the oscillator and incoming syncpulses from a suitable sync separatingA circuit.v The reactance tube unit will belfound to be.lcontr'olled by the development of a' direct. current pulse or signalv which is derived from' changes in. phase occurring between the impressed incoming syncpulse-and the' oscillation frequency offthe sinevwave gen.- erated by the oscillator. The oscillator .f-requency, then, in turn,v may be Vmodified under.

the control of the reactance tube to which. the developed D- C. control'voltage is applied' to vary the reactance tube gain. and. thus bring. about a change in the reactance of' .the oscillator. tank circuit so that the oscillator frequencyl isbrOught into proper relationshipto the, incoming sync pulses and stabilized(oscillations, bearing a fixed..

relationship to the incoming. sync pulse; arcobtainable. The electronbeam deflection circuits proper of the cathode. ray 'tube-then. are' con.-

trolledrin turn, from control pulsesderivedfroin.

the stabilized local oscillator... l

In its. preferred form, the'inventin will=lbe illustrated as particularly applicable to a. deflec'- tion controlv system for cathode ray beams, .where.

theeiect of operation is illustratedas-applica-.

ble to the high frequency or line ,d'eectiontraces The block diagram ofEig 1T shows the invenvention schematically combined withv a t'elz'evision.Y

receiver unit. There theinco'ming, signals,.lin.l

cluding the video andV all' necessary'accompanyin'g synthesizing signals, as well. as Vaudio;where desired, arefirst. supplied to Vtheusual amplifier,

selector and converter unit,l the output. signals from which are then arifuoliietl ini any. vsuitable intermediate frequency ampli'er device.. Tha. amplified signals are then demodulatedin. a unit.`

marked asV the secondA detector to be, passed through a suitable video amplifier (usually with-A D. C. level setting. provided) to control theli'mage reproducing tube in such va, way. that thecath'ode ray beam. produces an. intensity modu lated pattern or raster on the tube`target. This recreat'es the originali imageY light'` values..

The detected signalsare alsosupplied. toa sync i signal separator to. select betweenthe Videoland...

synthesizing signals.

Since this inventionis priA marily applicable to. the horizontal lorline q de,

ilectlon control it will be assumed that the ve1 tical (field or frame) deection signals are then suitably selected to control the slow speed cathode ray beam deilection through any known form of vertical deflection control, such as the block ing oscillator and output. tube arrangement described 'by Tolscn et al.. in'. U. S. Patent No. 2,101,520; granted December '7, 1937. The other components so far explained and mentioned are vwell known in general and require no further explanati'on'.

The selected horizontal (that is, the line pulses for providing` a. controlof the rapid motion of the cathoderay beam) are then supplied, as above rstatedpto the-discriminator unit 35 to which the output of the local deflection control oscillator 5i is also supplied, such as above stated. A reactance tube unit il? is connected across the oscillator tank circuit to change the oscillator frequency with output changes from the discriminator being, suppiled-to the reactance tube. unit tcrvar'yl Vits`trahscond'uctance and, in accordancey wi'thffrequency changes thus broughtabouigthe.v local oscillator is caused to Ifollow the frequencyIv anjdl. phase changes in thecontrolling4 pulses` Further 'details ofthis-controlwill be mentioned.

A lflorizontal"` dei flectio'ncontrol unit1 is arranged t'o controlthe lin'e'or horizontal" deflection of. the cathode ray `be'anfri ofthe'i'mage producing Vtube when the out--r `put'signallenergyfrom the local oscillator is supplied'f as indicated.. as `willlater be explainedlin..

in describing the actual circuit.

more detail.

The" circuit' diagrammatically represented.by` Fig. 21's one' practical' embodiment ofthe schematic showingof Fig. l' and illustrates the input. terminali Il ast-li@ point at which incoming synchronizing or sync 'signal pulses (conventionally represented .above the terminal as the'line synsons of simplicity, vthe verticalv inputv sync pulses.

are. not shown, althoughwin normal present. day

operation, botlrth'e vertical. andi the horizontal. or line syncpuls'escorrespond to those proposed and recominendedby the' industry and by the National Television' System-.Committee andwhich. are" found exemplied and'shown on` pages. 2-2

andv 2K3-"of the'bookentitled, Television Stand#- ards andPractic'e-by Donald G..Fink`,.publi'shed byMcGraw-Hill'Book Company, Inc., New York,

1943i r4In Vthis`form,"the"sync signalsv represent those whichJhave been r'ecommendedby the Na. tionalTelevision' System Committee andit'spanillustrations herein given are applied;V for. simA plivcity.,v to' thenew standardized signal form.

Thein'coming signal; pulses are normally ap..

plied torthe control grid of the Syncseparator tube' l5" bywayof' the 'small condenser il'.

The sync Separator tube i5 functions in itsf operation in known manner to separate the sync signalA .pulses from any -remaining portions of the signal. OperatingN voltages for sourceis showni in'.- detail by v the.- drawings but in each..instance the: sourcefis connected with' chronizin'g pulses a and b) are applied. For. reaf The cathodelg` of 'the sync separator tubeis preferv. ably/connected to: ground, .which is convention-.y

l the sync:v separator.l tube legare appliedthroug-h the load' resistor 24' from a source of voltage (no-voltage alledrie.

indicated polarity and the other source terminal may be assumed to complete the D. C. path through ground) which is connected with its positive terminal connected to the terminal point 25. Any high frequency outputs from tube l may be bypassed around a portion of the resistor 24 by way of the high frequency bypass condenser 21.

.Output signals from the tube |5 are then supplied by way of a condenser 29 to the conductors 3| and 33. The wave form shown above the tube I5 thus is any representative form of input and not necessarily that applied to the terminal point In the description to follow, the sync pulses will, for reference purposes, be assumed to be positive in the output of the tube l5 as indicated by the arrow on Fig. 2 of the drawing. As similar application of the signal with the image information removed is indicated bythe arrow on Fig. 5.

The output energy (or pulses) which appears from the tube I5 and which is applied to the conductors 3| and 33 is then fed to a discriminator tube 35, of which the operation will later be described.

At the same time that line frequency sync pulses, such as a and b, for instance, are being applied to the discriminator tube 35, the frame or eld frequency sync pulses, which are of relatively long duration, as is well known in the art, and which are supplied also to the sync separator tube l5, are fed through the conductor 3l from the output of the tube I5 to control the field or frame deflection control system (not shown) of the apparatus.

The line frequency signals, which are fed by way of conductor 33, are then connected to the center tap 39 of the transformer winding 4| which is to receive a signal from the local oscillator, later to be described. The transformer winding 4| forms an inductive element which is shunted by a capacity 43 and caused to resonate at a frequency which is slightly different than that of the local oscillator, later to be described. Tuning may readily be accomplished, for instance, by the indicated movable iron core, or any other suitable method may be chosen in the alternative. The difference in resonance frequency between the oscillator tank circuit comprising the inductance 53 and the capacitor 55 and the secondary winding 4| of the transformer and its shunt capacity 43 is made use of to obtain a desired phase shift between the oscillator voltage and the sync pulse as appearing at the input terminal This phase shift makes it possible readily to correct the phase between the differentiated discharge pulses, later to be described, and the incoming sync pulse which is obtained whereby a convenient means is provided to correct the picture form.

Thus, the sync or deflection control pulses, which are applied by way of the conductor 33 to the transformer winding 4| are, in turn, supplied to the plate or anode electrodes 44 and 45 of the discriminator tube 35, which plates or anodes are connected to the opposite ends of the transformer winding 4i. It will thus become apparent that the incoming sync pulses are applied to each diode plate 44 and 45 in equal amplitude and in phase with each other. Cathode elements 46 and 4l comprise the other electrodes of the tube 35, so that the anode 44 and cathode 46 together form one unidirectional conducting path and the anode with cathode 41 forms a second unidirectional conducting path. In other words, these electrodes collectively form two separate diodes which, for convenience of illustration and, usually, in operation from the standpoint of cost and convenience, are includedin one separate tube envelope. A tube of this type may be one of the form which is known in the art as the 6H6, which is a metal tube and which may have its outer shell grounded.

Two resistor elements, indicated as 48 and 49, are connected to the individual cathodes 46 and 4l with their other ends being connected together and also connected to the conductor 3| to which the sync pulse is applied, as above indicated.

The local oscillator hereinabove mentioned preferably comprises a tube 5| which is usually in the form of a tetrode and, for example, may be a. tube oi the type known in the art as the GKGGT, although this reference, like that given for the discriminator tube, is purely by way of example of one suitable form of tube for the use in question. rI'he oscillator tube 5| is caused to develop substantially sine wave oscillations in a manner which is substantially well known in the art and which may be considered as having been illustrated, in general, by the form of oscillator known as the Hartley type. The oscillatory circuit of oscillator .2| comprises an inductance element 53 which forms the primary winding of the transformer which feeds energy to the secondary coil 4i, hereinabove mentioned. The inductive element 53 is shunted by a capacity 55 so that oscillations may be considered as being developed in the circuit at a frequency determined by the inductance and capacity elements. The control electrode 5l of the oscillator tube connects to one endk of the oscillatory circuit. The cathode 58 connects to a central point on the inductance element 53. Lastly, the screen electrode 59 connects to the other end of the inductance through the connection made by way of the coupling condenser 5| and groundy 2|. Thus, a variance in the characteristics of the circuit elements included across the grid to screen grid path will provide oscillation frequency changes, and any oscillations appearing in the oscillatory circuit comprising the inductance 53 and the capacity 55 will, in turn, be transferred by way of the secondary winding 4| to apply voltage to the plate or anode elements 44 and 45 of the discriminator tube 35.

Tuning may be provided, 'where desired, for the coils 4| and 53 by way of the indicated adjustable iron core elements, as is known in the art. In the manner in which the invention has been shown, it will be apparent that if the oscillatcr is tuned to approximately the frequency of the incoming sync pulses, such as a and b, stabilized oscillations will be developed. In this sense, stability is readily improved by making the capacity 55 relatively large in size. If sine wave voltages are induced from the primary winding 53 into the secondary winding 4|, it will be observed that these voltages appear out of phase with respect to each other, as applied to the diode vplates 44 and 45. It has been seen, from the above explanation, that the separated sync pulses, as appearing in conductor 33, are applied to the center tap 39 of the discriminator coil 4| and, accordingly, appear in phase on each of the plates or anodes 44 and 45 of the discriminator tube 35.

This state of conditions may readily be ob- A, the indicated sine wave voltages are intended 2er-soffia t6 Tresi-ferent me voltage the diede secties' '4 4", due to the oscillator l', While the curve Bof Fig.v 3 s.- Ws by'its sine Wave curve the 1 80' out' of phase 'ifoltagerap'plied to th 1di'de section'135, 41 into the oscillator 51. If :it be asd that thesync pulse indicated as a is such that relative phase ofthe sine Wave voltages 'and the' sync pulse appear Aas shovl'nb'y Fig. 3,the'i, ese sentially, a zero D. C. output Will appear at the point S2 to be supplied by Way of tlrendieated conductor 65 to control the vreactance t'u S3, later to be referred to more "spec'iic'ally.` Y

Should the relative' phase' f the rvoltages ai)- plied to the diode sections 'due Ato th oscillator and the' voltages applied Vdue to the incoming sync pulse change, as indCatedbyltH 'secoidv condition shown by Fig. 4 Where the fsyri puls ais now assumed to lead slightly with regard to its position shown in Fig. 3, it will be apparent that incre voltage Will be produced across' the top diode load t8 than appears across the lower ydiode load ce? for reasons which appear to be ireadily apparent when the curves on Fig. '1l (A) .and Fig'. fi (B) are considered.

If the sync pulse'a moves vto the Aright from the position shown, it will be apparent by the Vsame' reasoning that'rnore voltage appears across 'the lower diode output resistor fis across the upper diode output resistor '48. No particular relative relationship has `here been cho-sen ior the incoming control vsync pulse and the sine wave voltage but it should be under; stood that in many instances preferred operation is had'when the pulse voltage (such as the pulses' a and b, and so on) exceeds the 'peaket'ope-at:v

voltage of the sine Wave outputof 'the oscillator as supplied to the diodes.

Depending upon which diode sectionv of the' discriminator produces the greater Voltage de= pends the relative polarity ormagnitude of the oscillatory circuit comprising the Winding 55 andY the condenser 55.

With the arrangement shown whereby the voltage developed at the point 512, orin'stance, is supplied to control the reactance tube i3-by Way of the grid feed resi-stance and the capacity, it Will be observed that a lter and time constant circuit has been provided. The general `effect of such a time constant circuit and lter is to lter out any low frequency A. C. from the D. C. control voltage. Such lowirequencyA. C. might, under some circumstances, come about'due to thevertical sync pulses, to name one example.

The cathode of the reactance tube 63 `connects to ground 2| and, thus, to the other end Yof the oscillatory circuit. The plate 19 of the reactance tub-eGS connects by Way o condenser 8| to the grid or control electrode -51 of tube 5I through the usual grid leak and condenser circuit 32,

From what has been abovejshowrr it will be apparent vthat VYthe control voltage appli-ed to the control electrode 59 of the reactance tube (i3-is such as to restore the original balance Ycondition tothe system should the phase of eitherthesyn'c pulse or the oscillator change within the limits of the systernE `From what has been 'aboved'escribed, it will beapparent that the-reactance tube $3 acts as a shuntreactance lacross the osthan appears .411 Voltage'which appears at point 32 4and which i'is brought about by a' 'Variation of :the fCD. C2 iift' applied to yth control lelectrokle69 lnfacdoiidanc? with tlie 'variation 4of diode-of th' dis# crirnnator draws' thnlor current.

The reactance tube B3 is so set up that' 'the ractance 'varies thev'direction to keep tlfiis- Ciltor '51! in Iphase 'With the "Pulse appld" a :source of voltage (not shown 'is 'connected with its positive terminal connected to the ter#- minal point 285. The 'same source of yoltagepd vides the operati-ng voltage `which's' suppli'edfto tlle'screen electrode '59 ofthe oscillator tubefbyw way or" the connection to -i't through the' resistor In the arrangement shown, it will be under- ,st-ood that 'ali voltages represented Vvby the plus connections 'at various terminal pointsfare'un-V derstoodl as beingv so connected that thefpositver terminal connects as indicated andthe -neative terminal connects to ground-to 'provide the direct current path, 'Which'l'l'ias lnot Abeen shown completed'"throughout for convenience of illusie trato'n. Y

The oscillator tube 5l so functions Aas to produce plate current saturation at the anode'83`dury-r ing theipositive half cycles. The'result is that the plate voltage appearing at ythe `plate Yoranode B3;

under these circumstances, is essentially and-for allpractical purposesy a square Wave, as Iindicatedby the Wave forni exemplified adjacent 'the tube output. This youtput wave -is then lfed'orsupplied through -adifferentiating circuit comprising the cond'enser' and resistor-'83 vconnected 13o-ground 2 l, and coupled tol this differentiating circuitby way o f condenser -89-is the control electrode-SU of' a discharge tube fl. Through the utilization of 'the dierentiating circuit, comprising the con* denser 3;? 'and the resistor e8, a. narrow pulsa-as indicated by the Wave-form adjacent the diagram, is developed to actuate the discharge tube. The discharge tubelil `is self vbia-sed by way of there sister 92 and its plate or anode' connects by way of the resistor'elernent S3 to the positiveterminal'of a source of'voltage (notshown) Which/is The voltage source which lconnects at terminal i is then arranged to charge lthe condenser gg'through the l:charging resistor or output resistor of tube Sl-so that a voltage Wave appears across the condenser between the terminal and ground Whichfisin theugeneral shape of a vsawtooth.

This -sawtooth Wave has its relatively low slope portion representing anfincre'ase -in voltag-e'across the condenserpla-tes built up by charging vof the condenser 99 through the resistor 96. The steep slope or discharge Vportion of the condenser is occasioned during the p eriod YofV conductivity withinthedisc'harg'e tube Si as produced by the positive portion or the differentiated vpulse "that is appiied 'tio theizontrcl 'grid '99, Thus.' sav/toorn vin known manner. "practice, theotput tube-- heretofore not mentioned; Thefano'de or plate' 83 eonnects'through 'theroutput' or load resistor 84 to 'a terminal point I85 whereas 1 Vcondenser 6I.

IUI is usually a pentode or a tetrode and especially so where the system operates at line frequency. The triode illustrated is merely shown for convenience of illustration. The output tube supplies the output pulses to the primary winding H of the transformer Iil Where the output load is in the form essentially or the output coil through which the positive potential for the output tube IIJI is provided from a terminal point IBS which connects lto a positive terminal of a voltage source (not shown). The secondary winding IHS of the output transformer connects at its ends to the output terminals i IB and i I I to which the suitable deflecting coils (not shown) are arranged to be connected in known manner.

Fig. 5 shows a modification of the circuit of Fig. 2 and like parts in each Figure are referred to by like reference nulnerals. Similar to the circuit arrangement of Fig. 2, the incoming sync pulses, preferably of positive polarity as indicated, are applied to the input terminal II and then fed in an iii-phase manner upon each diode. In contrast to the direct connection between point 39 and the junction of resistors 48 and 49, as shown by Fig. 2 it has been found desirable in many instances to include more resistance at this point in the circuit, which resistance is provided by resistor unit 52. Likewise, in some instances it has been found desirable for increasing operational delity to apply a relatively low negative bias to the cathodes of the discriminato-r by connecting a. suitable bias voltage at the terminal point 5G.

As was explained in connection with the arrangement of Fig. 2. the oscillator tube 5I is connected in such a way that the oscillatory action takes place between the screen grid 5S and the cathode 58. It is usually preferable to couple Vthe oscillator coil 53 rather tightly to the center tapped coil il which, like in the arrangement of Fig. 2, is preferably adjusted to a slightly offresonance condition through the use of an indicated movable iron core.

As was explained in connection with Fig. 2, this arrangement is such that if the phase of the incoming sync pulses applied at terminal II, for instance, is changed with respect to the sine wave output of the oscillator tube 5I, as applied to the oscillator coil 53 and the coils III, one or the other diode half of tube will produce a greater voltage drop across either resistor 48 or resistor 49. It will be appreciated that if the greater drop of voltage takes place across the resistor 48 the voltage across the two diodes may be assumed to be positive, Whereas if the greater voltage drop takes place across the resistor 49, the opposite or reverse condition may be assumed to exist. Accordingly, the voltage developed at the point 52 which is to be used to control a gain of the reactance tube 53 can vary from a positive value through zero to a negative value dependent upon the phase relationship of the incoming Sync pulses and the sine wave output of the oscillator as affecting the discriminator tube unit 35.

In the arrangement shown by Fig. 5 the reactance tube S3 is connected in a slightly diierent manner with respect to the oscillator tube from that shown by Fig. 2. It will be seen that the oscillator tube 5I has its grid 51 connected to one end of the oscillator coil 53 and its screen grid 5S connected to the other end of the oscillator coil, which end is grounded at 2i, through the The oscillator tube cathode 58 connects to an intermediate point of the coil 53. The

.reactance tube is so connected that its pla-te 'I9 which is supplied by positive voltage from a terminal 'I2 through the indicated resistor connects to one end of the oscillator coil by way of condenser 8I. The cathode of the reactance tube connects to the junction point 64 between the oscillator tank circuit condenser 55 'and resistor 50 which are serially connected across the oscillator coil 53. In this Way, quadrature Voltage is supplied by conductor |25 to the reactance tube, as indicated.

Under these conditions it will be a-ppreciate that the D. C. output available at the point 62 is now supplied by way of the conductor 66 to the grid or control electrode 69 of the reactance tube and superimposed upon a fixed bias applied to the same electrode through the lter comprising the combination of the resistor B'I shunted by condenser I I4 and across which the condenser II5 connects to ground. The reactance tube operates to provide a reactive plate current by virtue of the cathode input sine wave Voltage obtained from across the resistor 60 which is in series with the oscillator tank capacitor 56, as above explained. Any changes in the D. C. Voltage applied in conductor 66 to the grid 69 of the reactance tube by virtue of Voltage changes appearing at point 62 tend to provide changes in the transconductance of the reactance tube B3 and thus bring about changes in the reactive plate current, since the plate I9 of the tube 63, as above explained, connects with the oscillator tank coil 53 by way ofthe condenser 8l.

Accordingly, as was the case with -the circuit ofFig. 2 Where the phase of the oscillator is not in proper relationship to the incoming sync pulse applied at the terminal I I, the D. C. information obtained from the discrimnator will correct the oscillator frequency and'cause it to coincide with the control pulses.

In the arrangement shown by Fig. 5, the lter combination comprising the resistor 61 and the condensers II4 and I I5 is such that the two condensers form a Voltage divider to attenuate rapid changes in direct current, such Yas are produced by the vertical sync pulses orA bursts of interference and, thus, this further .tends to stabilize the oscillation frequency. It has been found that Where the transmitted sync signal pulses are not sufficiently stable, which is a condition that, unfortnunately, exists at times, a relatively flat response to fluctuations in the D. C. information is required.Y This is obtained in this circuit by a proper determination of the ratio of the size of the condensers |I4 and II5.

In addition, Where any considerable degree of instability of the incoming control pulse frequency exists, it is 'often desirable to provide further .control measures. 'Io this end, the filter combination above described is provided with an additional shunting capacity I I6 of which one terminal connects to the ungrounded terminal of the capacity I I5 and the other terminal connects to the switch arm II8. Under normal operating conditions where there is relatively good stability in the incoming sync pulses the switch arm II8 is placed in its upper or open position against the terminal |22, as shown, but where considerable instability in the incoming sync pulses is found to exist, the switch arm II 8 is moved to the lower or closed terminal |20 position whereby the condenser I I 6 is placed in shunt with the condenser I I4 and the response of the circuit increased. Y

The manner of deriving a substantially square weve Output from the oscillator tube 5I is subelement, connecting circuit elements for applying the triggering pulses to the discharge tube whereby the stored charges are dissipated and a substantially sawtooth voltage wave of a frequency corresponding to the sine wave oscillator is developed across the storage means, and a load circuit including the deecting elements of the cathode ray tube connected to receive the said developed sawtooth voltage wave for deecting the cathode ray beam.

3. In electronic apparatus wherein deection voltages are to be developed to deflect a cathode ray beam under the control of a series of control energy pulses subject to slight frequency and phase changes, a local oscillator for normally developing substantially stable sinusoidal oscillations at a frequency substantially coinciding with the normal desired repetition frequency of the control pulses, a detector unit including a pair of unilaterally conducting devices, means simultaneously to apply the sinusoidal oscillations to the two unilaterally conductive devices as two out-of-phase waves, means to apply the control pulses to each unilaterally conducting device in an n-phase relationship whereby at times of frequency vand phase identity between the control pulse repetition and the sine wave oscillations a predetermined output is derived from the detector unit and with phase shifts of the control pulse between a faster and a slower frequency of recurrence than that of the said sine wave oscillations the output voltages developed by one or the other of the unilaterally conducting devices become unequal and provide a changed value control voltage, reactive means to control the local oscillator frequency, means to modify the eifective reactance of the said reactive means to cause an increase or a decrease in the local oscillator frequency in accordance with the output voltage variances of the rectifier elements, and means to control the deflection of a cathode ray beam under the inuence of the developed sine wave energy and at a frequency coinciding therewith.

4. The apparatus claimed in claim 3 comprising, in addition, means to develop substantially square wave voltage pulses from and at the frequency of the said sine wave oscillator, a deflection control circuit including a storage element connected with a source of voltage so as `to be charged along a substantially linear path.

means for differentiating the said square wave pulses to develop triggering pulses at a frequency corresponding to that of the sine wave developed by the oscillator, discharge tube means connected in shunt with the said storage element, a connecting circuit for applying the triggering pulses to the discharge tube whereby the stored charges are dissipated and the voltage across the storage element is of substantially sawtooth form and of a frequency corresponding to that of the sine wave oscillator, and a load circuit including the deecting elements of the cathode ray tube connected to receive the said developed sawtooth voltage wave for deecting the cathode ray beam.

5. The apparatus claimed in claim 2 comprising, in addition, a deflection circuit having included therein means to develop substantially sawtooth form'electrical wave energy for use in deflecting a cathode ray beam in a selected direction, and means to derive triggering pulses from said oscillator output to initiate an operation of said deflection circuit. y

6. In ltelevision apparatus wherein deflection voltages'are to be developed to control the deflec- 14 tion of a cathode ray scanning beam in synchronisin with a remote scanning operation, and wherein the scanning control pulse energy to control such operation is subject to slight frequency changes as a result of a remote operation, a normally stable local oscillator means for developing substantially sinusoidal shaped oscillations at a frequency substantially coinciding with the average repetition frequency of the control pulses7 a detector unit including a pair of unilaterally conducting devices, means simultaneously to apply the sinusoidal oscillations to the two unilaterally conducting devices in push-pull fashion, means to apply the scanning control pulses in an in-phase manner to each unilaterally device whereby at times of frequency and predetermined phase identity between the control pulse repetition and the sine wave oscillations a predetermined output is derived from the detector unit and with phase shifts of the control pulse between a faster and a slower frequency of recurrence than that of the said sine wave oscil- 1rations greater output voltages are developed by one or the other of the unilaterally conducting devices, a reactance tube unit connected to control the local oscillator frequency, means to vary the gain of the said reactance tube unit to modify the effective reactance thereof and thereby to cause an increase or a decrease in the local oscillator frequency in accordance with output variances of the individual unilaterally conducting devices due to phase diiferences between the applied control pulses and the generated sine waves which represent a relative frequency increase or s decrease of the control pulses. and means to control the deflection of a cathode ray beam under the influence of the developed sine wave energy and at a frequency coinciding therewith.

'7. In television apparatus wherein deflection voltages are to be developed to control the deflection of a cathode ray beam in synchronism with received control synchronizing pulses which are subject to frequency repetition changes in accordance with a remote operation, a detector unit including a pair of unilaterally conducting devices, a local oscillator including a tank circuit wherein substantially sinusoidal oscillations are developed at a frequency substantially coinciding with the normal repetition frequency of the developed control pulses, means simultaneously to apply the sinusoidal oscillations to the two unilaterally conducting devices as two out-of-phase waves, means to apply the control synchronizing pulses to each unilaterally conducting device in like phase relationship whereby at times of frequency identity between the control pulse repetition and the sine wave oscillations a predetermined output is derived from the detector unit and with phase shifts of the control pulse between a faster and a slower frequency of recurrence than that of the said sine Wave oscillations greater voutput voltages are developed by one or the other of the rectifier elements, reactance means connected in shunt to the oscillator tank circuit to control the local oscillator frequency, means to modify the effective reactance of the said reactance means to cause an increase or a decrease in the local oscillator frequency in accordance with output variances of the unilaterally conducting devices due to frequency increases or decreases in the control pulses, and means to control the deflection of a cathode ray beam under the influence of the developed sin'e wave energy and at a Jfrequency coinciding therewith. v

13. A circuit for providing deflecting wave ens ergy to lbe supplied to deilecting means for controlling the deflection of a cathode ray beam de veloped within a cathode ray tube insynchronism with remote effect which comprises means including a storage element and a discharge tube connected thereto vfor, developing substantially sawtooth wave energy adapted to be supplied to control the beam deflecting means, means for deriving, pulse energy occurring at a frequency at which it is desired that the said deflection shall occur, a local oscillator having a tank circuit wherein substantially sine wave voltages occur, means for deriving triggering pulses from the said sine Wave voltages so as to trigger the discharge tube at a rate corresponding to the sine wave frequency, means for developing two outof-phase like frequency sine waves from the said oscillator, means for additively and repeatedly combining each of the derived pulses representingthe desired' deflection 'frequency and the said out-of-phase Waves, a phase detector unit for making a phase comparison between the fre- Y.'

quency of repetition of the developed sine waves and the developed pulse energy so that output voltages are derived from the detector which are proportional to advanced and retarded phase relationships betweenthe derived control pulsel en- 3 ergy and the sine'wave frequency, a reactance tube means having its output connected to the oscillator and its V'input connected to respond both to quadrature voltage derived from the oscillator and the output of which serves to vary the reactance tube gain and provide a reactive current to modify the frequency of the local oscillator to a value at which it substantially coincides with the frequency of recurrence of the developed pulses.

14. A circuit for providing deilecting wave energy to be supplied to the electron beam deecting means of a cathode ray tube for controlling the deflection of the developed beam in synchronism with a remote effect which comprises a local oscillator having a tank circuit wherein substantially sine Wave voltages are developed, means for deriving triggering pulses from the sine wave voltages for initiating deflection of the cathode ray beam in substantial frequency coincidence with the sine wave frequency developed by the local oscillator, means for deriving voltage pulses at a pulse repetition frequency corresponding to that of a remote source which represents the frequency at which it is desired the said deflection shall occur, a detector unit including a pair of unilaterally conducting devices, means simultaneously to apply the developed sinusoidal voltages and the derived control voltage pulses additively to each unilaterally conducting device of the detector unit so that one of the two voltages is applied to each unilaterally conducting device in an out-of-phase manner and the other of the two voltages is applied to each unilaterally conducting device in an in-phase manner so that for a predetermined phase relationship existing between the two voltages a predetermined voltage output is derived from the detector unit and with phase shifts of the derived control pulse voltage between a faster and a slower frequency of recurrence than that of the normal frequency of the sine wave voltage greater or lesser output voltages are derived from each unilaterally conducting device of the detector unit, a reactance tube unit having its out- 18 put coupled across the oscillator tank circuit, means to supply voltage from the oscillator tank circuit to an input electrode of the reactance tube meansand in a predetermined phase re- -lationship with respect to the voltage supplied from the oscillator to the detector unit, means for applying a predetermined bias voltage on the input of the reactance tube to control the current normally flowing therethrough, and means to modify the voltage bias upon the reactance tube in accordance with variances in output from the detector unit so as thereby to vary the transconductance of the reactance tube and thereby vary the reactive current effective upon the oscillator tank circuit and cause the oscillator frequency to vary in a ldirection to coincide with that of the derived control pulse signal voltages.

15. A circuit for providing deflecting wave energy to be supplied the electron beam delecting means of a cathode ray tube for controlling the deflection of the developed rbeam in synchronism with a remote elect which comprises a local oscillator having a tank circuit wherein substantially sine wave voltages are developed, means for deriving triggering pulses from the sine wave voltages for initiating deflection of the cathode ray beam in substantial frequency coincidence with the sine wave frequency developed by the local oscillator, means for deriving voltage pulses at a' pulse repetition frequency corresponding to thatl of a remote source which represents the frequency at which itis desired the said deflection shall occur, Aa detector unit including a pair of unilaterally conducting' devices, means simultaneously to apply the developed sinusoidal voltages and the derived control voltage pulses additively to each unilaterally conducting device of the detector unit so that one of the two voltages is applied to each unilaterally conducting device in an out-of-phase manner and the other of the two voltages is applied to each unilaterally conducting device in an in-phase manner so that for a predetermined phase relationship existing between the two voltages a predetermined voltage output is derived from the detector unit and with phase shifts of the derived control pulse voltage between a faster and a slower frequency of recurrence than that of the normal frequency of the sine wave voltage greater or lesser output voltages are derived from each unilaterally conducting device of the detector unit, a reactance tube unit having its output coupled across the oscillator tank circuit, means to supply voltage from the oscillator tank circuit to an input electrode of the reactance tube and in a predetermined phase relationship with respect to the voltage supplied from the oscillator to the detector unit, means including a filter combination comprising resistance and capacity elements for applying a predetermined bias voltage on the input of the reactance tube to control the current normally flowing therethrough, and means to modify the voltage bias upon the reactance tube in accordance with variances in output from the detector unit so as thereby to vary the trans conductance of the reactance tube and thereby vary the reactive current effective upon the oscillator tank circuit and cause the oscillator frequency to vary in a direction to coincide with that of the derived control pulse signal voltages.

16. A circuit for providing deflecting wave energy to be supplied the electron beam deflecting means of a cathode ray tube for controlling the deflection of the developed beam in synchronism with a remote effect which comprises a local oscillator fhavinge Atank circuit whereinV Vsubstantially-sine wave voltages lare developed, -means for deriving triggering Ypulses @from -the fsinel 'wave voltages for initiating `deflection of thewcathode ray beam Vin substantial frequency coincidence with the vsine wave frequency developed bythe local oscillator, means for-deriving pulses :at pulse repetition frequency Acorresponding to that ofV a remote source which represents the frequency vat which it is vdesiredthe sad-deectionrshall occur, i

a detector vunit including 'apair fof unilaterally .conducting devices, means simulltaneouslyV 'to apply the developed 'sinusoidal voltages and the derived control Avoltage pulses additively `to each unilateral-1y conducting device of tldedetector unit so that one Aof ythe Y'two voltages is `appliedto each unilaterally `conducting y-device 'in a push-'pull manner and the other of the two voltages is applied to Yeaclrof the 'unilaterallyconducting de- -vices a Ypush-push manner so that for a.l "predetermined Ap'l'iase vrelationship existing between the two voltages a predetermined voltage output is `derived from the detector-unit and YWith'phase shifts -of the derived controlpulsevolta-ge 'between a faster and a slower -frequency -o recurrence g."

than that of the normal -frequency lof 'the sine Wave voltage -grea-'ter Lor lesser output voltages are derived from yeach unilaterally conducting device of the Vdetectorun-it, a reactance tube unit having its output -coupled across the `oscillator 'tank circuit, means to supply voltage from the oscillator tank circuit to an Linpl-itelectrode'of the reactance tube means and-in a predetermined Vphase re- S520 llfationsniplreiativefte 'voltage supplied to the detector unit, means :including ialilter combinavtion "comprising "resistance and xcapacity elements vthat -of the derived `control'pulse signal voltages,

and switching means vto modify the capacity lvalue fof the 'bias :setting time constant -crcu'ift to ccmtrol thereby `the rate fat which thev effectiveness of the detector unit applied to the 'reactanee tube toyarythe gain thereof may ibe varied.

v`ANTONYNVRIGHT. EDWIN .L CLARK.

REFERENCES CITED 'The following .references =are of record inthe 'le of this patent:

-UNITED STATES PATENTS 'Number Name Date 1,933,219 Nakajima Oct. 31, 11933 2,230,926 Bingley Feb; 4, i941 2,335,265 Dodington Nov. A30J :194'3 2,389,025 Campbell Nov. 13, 1945 

